1. Field of Invention
The present invention relates to an apparatus and method for performing a chemical vapor deposition. More particularly, the present invention relates to an apparatus and method capable of performing a chemical vapor deposition at a lower reacting temperature.
2. Description of Related Art
Chemical vapor deposition (CVD) is a technique for forming a solid thin film on a substrate by the chemical reaction of one or a few types of gaseous reactants. Because most common participating gaseous reactants are fluid, fluid flow phenomena affect the performance of a CVD reaction.
Laminar flow and turbulent flow are the two most commonly observed fluid motions. The speed and direction of flow of the former is smooth while that of the latter is non-uniform and chaotic. In general, when the diameter of a pipe in which a fluid moves through is wide, or the speed of flow is high, the fluid will flow in a turbulent mode. However, turbulent motion of the gaseous reactants is highly undesirable for chemical vapor deposition. This is because a turbulent flow will stir up micro particles or dust particles within the reaction chamber so that final quality of the deposited film is adversely affected. Therefore, most CVD equipment design tends to incorporate a smooth laminar flow section in its reaction chamber so that reaction stability is maintained.
Generally, if the flow of gaseous reactants in a CVD process is laminar, a higher deposition temperature must be used. A higher temperature not only increases power consumption of the CVD equipment, but also can easily damage silicon chip structure causing reliability problems, especially when a high temperature is used in the later part of the manufacturing cycle. Alternatively, a deposition process capable of being performed at a lower temperature, such as a plasma-enhanced chemical vapor deposition (PECVD) method, can be used. However, it is difficult for a PECVD method to deposit a smooth and uniform thin film over a substrate. In other words, the deposited thin film lacks conformability.
In light of the foregoing, there is a need to provide a better apparatus and method for carrying out chemical vapor deposition.